Attention has been focused on a technique for forming a transistor using a semiconductor thin film formed over a substrate having an insulating surface (also referred to as thin film transistor (TFT)). The transistor is used in a wide range of electronic devices such as an integrated circuit (IC) or an image display device (display device). A semiconductor material typified by silicon is widely known as a material for a semiconductor thin film that can be used for a transistor. As another material, an oxide semiconductor has been attracting attention.
For example, Patent Document 1 discloses a technique in which a transistor is manufactured using an amorphous oxide containing In, Zn, Ga, Sn, and the like as an oxide semiconductor.